Preparation of dyestuffs of the dibenzanthrone series



can;

t oi ibluen'ess ofi the color due a a a class;

This mventionrelates to the preparation of I dyestuffs of the dibenzanthrone series and more and. improved process Xydibenzanthrone 2,140,415 5 """v I Hammer F DYESTUFFS or THE QDl l QEN ZANTHRQNE-SERIES Edward: Howell, matter, we; assig'mr" to v, p :EJL :du' Pont de Nemourscompany, Wilming ton; D l.-,,a,: corporation of-iklaware Qrawin giihpplication July 24,-

s r-1a; No., 155,5 1

potassium carbonate for sodium carbonatein Fthe ,ethylation; of dihydroxydibenzanthrone in nitrobenzenewith diethyl sulfate, a very desira- "ble greenish blue dyestufi can be obtained in good yields, the shade of the resulting dyestuff- 'f. v :Jo'ei'ng materially different from that of the prodalkyl sulfates in nate as .the. acid dimethoxydibeiizcotton in bluish I [green shades. "e dletlioxydibenzanthrone pre ipared by this process (Example I dyes cotton lief v' s w pl h dee t s: w e hat n re i t h kyd b nz T 92 ,thrqn dyes; cotton-in l i hl e te s ad a r iant flatnes n ope t esyb t on id ble d m- V c ahaszr cnacx ri nc ie fib m gfii pll siimc hoxvsiibenz nthr nei w en h ni th la o :i -ca riedicu n t obenz newitn dimet yi su .iate. in the presence of sodium carbonate; as more 'J I Patent 1,531,261. Due to the side reactions which apparently take place in the reaction causing the .formatiofiioit; impurities, whichvdye; ini extremely .bluish 'green-l-sliades, the final %dyes'tufi.:is1deflcient in tinctorial; poweri andfldyes in somewhat'rnore I bluish green than is d'esirable. Complete:- methylation of the dihydroxydibenzanthrone when h'sodiumcarbonate is employed is often impossible,

due apparently to aside condensation'g' so that -the shade of consecutive batches" of' color vary 'Everi the pure "diiritho' diben'zanthrone r idyes'irfvery bliiishgreenshadsfsd thatfincreased t: improper methyla- A 'tionis to beavoided, and ever endeavor made i f b edefin ?'wid esna fi e had 'berftamee dun f theyield and dyeing pro 'rt i of diniethoxy 55' plicant has also found that on the substitution ofzuct o'riginally described in U. S.- Patent 1,531,261. II'his discoverywas surprising in viewof the fact lthatthe substitution of potassium carbonate for sodium, carbonate as an acid binding agent in :this typeof condensation reaction does not ordinarily change the characteristics" of the resulting compound. In fact, in the alkylation of the same .dihydroxydibenzanthrone where alkyl halides are employed as the alkylating agents or where the I alkyl ester of ptoluene sulfonic acid is used, the substitution of potassium carbonate for sodium carbonate has not been found to give improved "results! 1 'I It-is therefore an object of this invention to provide' a-processfor the methylation of dihydroxydibenzanthrone in nitrobenzene or equiva- --lnt solvent with dimethyl sulfate by a procedure whichiwill give consistently yellower and brighter shades" than are'normally obtained by the process of U.' S.'Patent 1,531,261;

It is a further object of the invention to provide a simple and more economical process for the preparation of 'diethoxydibenzanthrone in which the 'ethylatio'n is carried out in nitrobenzene or equivalent solvent with an ethyl sulfate, to give a product that dyes cotton in bluish green shades of excellent fastness properties. v

According to my process the dihydroxydibenzanthrone, or partially alkylated dihydroxydibenzfanthrone, is suspended in a nitrobenzene with "finely divided potassium carbonate or bicarbonate "andheatedto alkylating temperatures with dimethyl sulfate (from 60 to 160 0. preferred, although higher temperatures may be employed) diethyl sulfate is used, somewhat higher temperatures may be employed.

This process is also applicable to the preparation of mixed ethers wherein one alkyl group may be introduced into the dihydroxydibenzanthrone molecule by any desired process, withsubs'equent completionfof the alkylation in nitrobenzene "using'dimethyl or diethyl sulfate in the presence of potassium carbonate. The free hydroxydibenzanthrone or the mono or disodium or potassium salt of the same may be employed as the starting material.

The following examples are given to illustrate the invention more fully. The parts used are by weight.

Example 1 An aqueous cake equivalent to parts of dihydroxydibenzanthrone (obtained according to U. S. Patent 1,866,501 or U. S. Patent 1,910,603) is heated in 500 parts of nitrobenzene with 25 parts of potassium carbonate dissolved in 25 parts of hot waterunder reflux of nitrobenzene, until practically all the water has been driven out and the temperature has risen to 150-160 C. After allowing to cool to C. or less, parts of dry finely pulverized potassium carbonate are added, and the temperature is raised to 'C.3and-'held while 60 parts of dimethyl sulfate are slowly added. When tests indicate completereaction, the mixture is allowed to cool to 25-30 (3., then filtered and washed with several portions of nitrobenzene. of solvent and the product which may -'then be isolated by an aqueous filtration gives. dyeings of excellent strength and great purity of shade.

Similarrsults are also obtainedif potassium bicarbonate is used in this example instead of potassium carbonate.

Example 2 a 26 parts of finely pulverized potassium salt of hydroxydibenzanthrone .(obtained according to Example'2 of U. S. Patent 1,950,366, using KOH instead of NaOH and starting from the initial material produced according to U. '8. Patent 1,910,603) suspended in 375'parts of nitrobenzene areheated -to'160 C. with 45 parts of potassium carbonate and treated during the course of 2 to 3 hours'with" 30 parts of dimethyl sulfate. The

reaction product, which is isolated as in .'Example 1, is of the same purity.

Example 3 diethoxydibenzanthrone is so obtained in a. relativelyhigh stateof purity, which dyes cotton in bright bluish green shades, somewhatbluer than the corresponding dimethoxydibenzanthrone.

Example 4 .50 parts of dichlorodihydroxidibenzanthrone .(obtained according to German Patent 546,678)

are treated as in Example 1, giving a product which dyes cotton in, bright blueshades.

Example 5 50 partsof the hydroxydibenzanthrone derivative obtained according to Example 18 of British Patent 401,645 omitting the treatmentwithalkavline hydrosulfite (oxidation product of the con- -densation product of dibenzanthrone with 1- chloroanthraquinone 2- carbonyl chloride, fol- .lowed by reduction with bisulfite) aremethylated as in Example 1. The product so 'obtainedldyes cotton in bright green shades.

Example '6 The filter cake is steam distilled-free Example 7 50 parts of hydroxymethoxydibenzanthrone in the form of an aqueous paste are dehydrated as in Example 1 in .500 parts of nitrobenzene with 112.5 parts .of potassium carbonate dissolved in water. After the dehydration, the mixture is cooled, 325 parts .of .finely powdered potassium carbonate ares-tadded, and the temperature raised -to '1'60 C. 37.5 parts of diethyl sulfate are then added. inportionslduring a period of 1 to 2 hours. After cooling, the reaction mixture is filtered. The methoxyethoxydibenzanthrone, which is isolated-as in Example 1, is of high technical purity and dyes cotton .in bluish green shades.

Example 8 An aqueouscake equivalent'to '40-'parts of dihydroxydibenzanthrone is heated with a potassium carbonate solution in .400iparts of nitrobenzene as in Example 1. The mass .is cooled'to 50 C. or lower. 72.parts of finely powdered anhydrous potassium carbonate and then 48 partsof dimethyl. sulfate are added, and'the reaction mix-v ture is heatedto 150 C. during .aboutone hour. Additional amounts of dimethylsul'fate are added if tests indicate incomp'letereaction. Theproduct maybe isolatedby. filtration or. steam distillationifollowed by filtration as in Example 1.

The reaction'ispreferably carriedout'in at least 10 parts of nitrobenzene for each .part of dry 'dihydroxydibenzanthrone. Theme of potassium carbonate has been found to 'permit'a"50%ireduc- 'tion in theamount of nitrobenzeneused in the reaction over the amount that has been found to bemost suitable with sodium carbonate, thereby making possible a material increase in the productionof the color per-unit of equipment. It also permits the use of 'a "less pure dihydroxydi- 'final color.

F I claim: 11. In the process :for preparing di'alkoxydibenzanthrones wherein aihydroxydibenzanthrone is alkylate'din'a nitrobenzene with a dialkyl sulfate of the class consisting o'f-dimethyl sulfate and diethyl sulfates, the step which comprises carrying out the'alkylation in the presence of a potassium carbonate. I

-2. The process for preparing dimethoxydibenzanthrone which .comprisesheating I dihydroxydibenzanthrone in-nitrobenzene withadimethylsulfate. and potassium carbonate at temperatures goo of from 60 to.160-.C.

v 3. The process .forqpreparing diethoxydiben- .zanthrone .which comprises heating vdihydroxydibenzanthrone. in nitrobenzene with diethyl sulfate and potassium carbonate v.at -.temperatures of from about to.1'85C.. 1

EDWARD "r. .HOWELL.

benzanthrone than can-be used withso'dium car- 'bonate, which .further decreases the cost of v the 

